SuperGroups - Groups with an extended activity stream

Description

What I would like to see is a feature for admins to create a super group. This group has the same functions as a regular Group but the activity stream displays not only group related information, but also "regular" activity from it's users.

The motivation behind this idea is that it allows international communities to create a super group which can display all the information from a certain country/region. A user can then visit www.mycommunity.com/groups/usa and he would have a complete overview of the updates in his homecountry. users could be added to the group automatically on signup when they pick USA as their country (auto group join plugin allows this)

I hope this could get implemented in the core or in the form of a plugin, I'll certainly ask around for people who might be willing to work with me on this one :)